A gel-limiting strategy for large-scale fabrication of Fe–N–C single-atom ORR catalysts

Abstract

Although transition metal single atom site catalysts (SASCs) show great potential for electrocatalysis, their large-scale controllable and flexible preparation remains a great challenge. In this article, we report a simple gel-limiting strategy for fabricating Fe–N–C single-atom catalysts and evaluate its feasibility in large-scale applications. The results show that the production of Fe-SASCs can be controlled by the limiting immobilization of a hydroxyl-rich temperature-controlled gel combined with simple centrifugal treatment, even if the amount of Fe-feeding fluctuates within a certain range. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS) confirmed the formation of Fe–N single-atom sites and the uniform distribution of Fe on commercial activated carbon. As an ORR electrocatalyst, the Fe-SASC delivered a higher limiting diffusion current, and more positive onset potential and half-wave potential (E_onset = 1.00 V, E_1/2 = 0.87 V), and excellent methanol resistance compared to commercial Pt/C (E_onset = 0.97 V, E_1/2 = 0.85 V). Using the prepared Fe-SASCs, a homemade Zn–air battery was assembled which demonstrated a higher open circuit voltage, power density, and stability, further proving the practical application value of our proposed method and as-prepared catalyst. More importantly, our reported strategy can be further developed and extended to the future preparation of more transition metal SASCs.